HW3 hints
1. First, remember that e=1.6x10-19 when you plug in numbers for the charges. The alpha particle has a certain amount of kinetic energy, and the closest it can get to the gold nucleus is when it has spent all of its kinetic energy at the expense of electrical energy required. At closest approach, the electrical energy between the alpha particle and gold nucleus will be equal to the initial kinetic energy of the alpha particle. At that distance, acceleration is force per unit mass, and there is only one force present ...
2. Use Gauss' law - the potential due to a spherical grain at a distance r, its radius, would be the same as that of a point charge of the same magnitude. That gets the total charge, and you know the charge of one electron.
3. Sum up the energy of all unique pairs. See this example from a previous homework set to get started.
4. If S1 is open, the battery is not connected to a closed circuit ... If S1 is closed, and S2 is open, C3 does nothing, since it is connected on only one end. This leaves you with two capacitors in series ... find their equivalent, and then find the total charge. What do you know about the charge on capacitors in series?
5. Remember that series resistors split the total supply voltage while parallel resistors have the same voltage. Remember that power is current times voltage, and power determines brightness. Given the same battery voltage in each case and the same resistance R for each bulb, find the voltage and current for each bulb to get the power and then rank them.
2. Use Gauss' law - the potential due to a spherical grain at a distance r, its radius, would be the same as that of a point charge of the same magnitude. That gets the total charge, and you know the charge of one electron.
3. Sum up the energy of all unique pairs. See this example from a previous homework set to get started.
4. If S1 is open, the battery is not connected to a closed circuit ... If S1 is closed, and S2 is open, C3 does nothing, since it is connected on only one end. This leaves you with two capacitors in series ... find their equivalent, and then find the total charge. What do you know about the charge on capacitors in series?
5. Remember that series resistors split the total supply voltage while parallel resistors have the same voltage. Remember that power is current times voltage, and power determines brightness. Given the same battery voltage in each case and the same resistance R for each bulb, find the voltage and current for each bulb to get the power and then rank them.
3 comments:
can we do number 3 in class?
can we also do number 1 part b?
ok
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